Lithium-ion battery and its electrolyte

Abstract

Compared with the prior art, the electrolyte of the present invention may form a stable CEI and SEI film on the surface of positive and negative electrodes, protect the interface between positive and negative electrodes, improve the acidic atmosphere of Lithium ion battery electrolyte, and reduce the damage effect of HF on the interface between positive and negative electrodes, thereby improving cycle life, high temperature storage performance, and safety performance of lithium-ion battery.

What is claimed is: 
     
       1. A Lithium ion battery comprising: a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode comprises a silicon-carbon composite and
 wherein the electrolyte is a Lithium ion battery electrolyte comprising an organic solvent, a lithium salt, and an additive, wherein the additive comprises a cyclic fluoro carbonate, a cyclic phosphazene, and a cyclic sulfate, the cyclic phosphazene has following formula: 
 
       
         
           
           
               
               
           
         
         wherein R 2 , R 3 , R 4 , R 5 , R 6  and R 7  are each independently selected from one of H, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a halo alkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms and at least two of R 2 , R 4  and R 6  are selected from a halogen atom, and 
         wherein the additive further comprises propylene sulfite (PS) that is present in an amount of 1 to 5% based on the total weight of the electrolyte. 
       
     
     
       2. The Lithium ion battery according to  claim 1 , wherein in the general structural formula I of the cyclic phosphazene, at least one of R 3 , R 5  and R 7  is selected from one of a halogen atom, an alkyloxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloalkynyloxy group having 2 to 20 carbon atoms, and a haloaryloxy group having 6 to 20 carbon atoms. 
     
     
       3. The Lithium ion battery according to  claim 1 , wherein the cyclic phosphazene is selected from at least one of the compounds represented by B1 to B18: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
       4. The Lithium ion battery according to  claim 3 , wherein the cyclic phosphazene is present in an amount of 0.1 to 10%, based on the total weight of the electrolyte. 
     
     
       5. The Lithium ion battery according to  claim 1 , wherein the cyclic fluoro carbonate has formula II: 
       
         
           
           
               
               
           
         
         wherein R 1  is selected from fluorine atom or haloalkyl group having 1-20 carbon atoms containing fluorine atom. 
       
     
     
       6. The Lithium ion battery according to  claim 5 , wherein the cyclic fluoro carbonate is present in an amount of 0.1 to 40%, based on the total weight of the electrolyte. 
     
     
       7. The Lithium ion battery according to  claim 1 , wherein the cyclic sulfate has formula III: 
       
         
           
           
               
               
           
         
         wherein R 8  and R 9  are each independently selected from one of H, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkenyl group having 2 to 20 carbon atoms, a haloalkynyl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a haloalkenyloxy group having 2 to 20 carbon atoms, a haloarkylnyloxy group having 2 to 20 carbon atoms and a haloaryloxy group having 6 to 20 carbon atoms. 
       
     
     
       8. The Lithium ion battery according to  claim 7 , wherein the cyclic sulfate is present in an amount of 0.1 to 8%, based on the total weight of the electrolyte. 
     
     
       9. The Lithium ion battery according to  claim 3 , wherein the cyclic phosphazene is present in an amount of 1 to 5%, based on the total weight of the electrolyte. 
     
     
       10. The Lithium ion battery according to  claim 5 , wherein the cyclic fluoro carbonate is present in an amount of 10 to 25%, based on the total weight of the electrolyte. 
     
     
       11. The Lithium ion battery according to  claim 7 , wherein the cyclic sulfate is present in an amount of 1 to 3%, based on the total weight of the electrolyte.